<!DOCTYPE html>
<!--[if lt IE 7]>      <html class="no-js lt-ie9 lt-ie8 lt-ie7"> <![endif]-->
<!--[if IE 7]>         <html class="no-js lt-ie9 lt-ie8"> <![endif]-->
<!--[if IE 8]>         <html class="no-js lt-ie9"> <![endif]-->
<!--[if gt IE 8]>      <html class="no-js"> <!--<![endif]-->
<html>
  <head>
    <meta charset="utf-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <title></title>
    <meta name="description" content="">
    <meta name="viewport" content="width=device-width, initial-scale=1">
    <link rel="stylesheet" href="">
    <style>
      dialog::backdrop {
        background-color: rgba(126, 201, 236, 0.6);
      }
    </style>
  </head>
  <body>
    <button onclick="dialog.showModal()">show</button>  
    <dialog>
      11111111111111111
      <button onclick="dialog.close()">close</button>  
    </dialog>
  </body>
</html>
<script>
  let dialog = document.querySelector('dialog')

</script>